<meta charset="utf-8">
(#) Short or Frequent Alarm

!!! WARNING: Short or Frequent Alarm
   This is a warning.

Id
:   `ShortAlarm`
Summary
:   Short or Frequent Alarm
Severity
:   Warning
Category
:   Correctness
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   1.3.0 (July 2015)
Affects
:   Kotlin and Java files and manifest files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/AlarmDetector.kt)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/AlarmDetectorTest.kt)

Frequent alarms are bad for battery life. As of API 22, the
`AlarmManager` will override near-future and high-frequency alarm
requests, delaying the alarm at least 5 seconds into the future and
ensuring that the repeat interval is at least 60 seconds.

If you really need to do work sooner than 5 seconds, post a delayed
message or runnable to a Handler.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/test/pkg/AlarmTest.java:9:Warning: Value will be forced up to 60000
as of Android 5.1; don't rely on this to be exact [ShortAlarm]
    alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME, 50, 10, null); // ERROR
                                                                 --
src/test/pkg/AlarmTest.java:11:Warning: Value will be forced up to 60000
as of Android 5.1; don't rely on this to be exact [ShortAlarm]
    OtherClass.MY_INTERVAL, null);                          // ERROR
    ----------------------
src/test/pkg/AlarmTest.java:16:Warning: Value will be forced up to 60000
as of Android 5.1; don't rely on this to be exact [ShortAlarm]
    alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME, 5000, interval2, null); // ERROR
                                                                   ---------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`src/test/pkg/AlarmTest.java`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers
package test.pkg;

import android.app.AlarmManager;
@SuppressWarnings("ClassNameDiffersFromFileName")
public class AlarmTest {
    public void test(AlarmManager alarmManager) {
        alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME, 5000, 60000, null); // OK
        alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME, 6000, 70000, null); // OK
        alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME, 50, 10, null); // ERROR
        alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME, 5000,  // ERROR
                OtherClass.MY_INTERVAL, null);                          // ERROR

        // Check value flow analysis
        int interval = 10;
        long interval2 = 2 * interval;
        alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME, 5000, interval2, null); // ERROR
    }

    private static class OtherClass {
        public static final long MY_INTERVAL = 1000L;
    }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/AlarmDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `AlarmDetector.testBasic`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("ShortAlarm")
  fun method() {
     setRepeating(...)
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("ShortAlarm")
  void method() {
     setRepeating(...);
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection ShortAlarm
  problematicStatement()
  ```

* Adding the suppression attribute `tools:ignore="ShortAlarm"` on the
  problematic XML element (or one of its enclosing elements). You may
  also need to add the following namespace declaration on the root
  element in the XML file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;manifest xmlns:tools="http://schemas.android.com/tools"&gt;
      ...
      &lt;uses-permission tools:ignore="ShortAlarm" .../&gt;
    ...
  &lt;/manifest&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="ShortAlarm" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'ShortAlarm'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore ShortAlarm ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

<!-- Markdeep: --><style class="fallback">body{visibility:hidden;white-space:pre;font-family:monospace}</style><script src="markdeep.min.js" charset="utf-8"></script><script src="https://morgan3d.github.io/markdeep/latest/markdeep.min.js" charset="utf-8"></script><script>window.alreadyProcessedMarkdeep||(document.body.style.visibility="visible")</script>